This invention relates to molecular beam epitaxy (MBE) and, more particularly, to a technique for localizing MBE growth to selected areas.
GaAs planar technology, as described by A. Y. Cho and W. Ballamy in U.S. Pat. No. 3,928,092 issued on Dec. 23, 1975, involves molecular beam deposition on a GaAs wafer covered by an apertured mask of an amorphous material such as SiO.sub.2. Semi-insulating polycrystalline GaAs deposits on the mask and simultaneously monocrystalline GaAs grows in the apertures (windows). Thus, monocrystalline and polycrystalline GaAs are selectively deposited on the wafer producing a planar pattern which consists of areas of electrically active devices (the monocrystalline zones) separated by semi-insulating polycrystalline GaAs.
Due to rapid innovation in microwave and optoelectronic technologies, there is a need for growing semiconductor materials on selected areas of a wafer or other growth surface. For instance, highly doped GaAs is desirable for the ohmic contact areas of a field effect transistor (FET), and Al.sub.x Ga.sub.1-x As is needed on the sidewalls of a GaAs junction laser in order to have two-dimensional optical confinement (i.e., a buried heterostructure).